Thin wrapper around wordnet sql database for getting definitions of words on iOS. Add the wordnet.sqlite3 file to your project and the sqlite3 dylib to the build phases. I downloaded the sqlite db from here: https://code.google.com/p/synonym/downloads

GABWordnet.h

//
//  GABWordnic.h
//  WordnicSqliteTest
//
//  Created by Greg Borenstein on 8/3/14.
//  Copyright (c) 2014 Greg Borenstein. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <sqlite3.h>

@interface GABWordnet : NSObject{
    sqlite3 *_database;
}

-(NSString*) definitionForWord:(NSString*) word;

@end

GABWordnet.m

//
//  GABWordnic.m
//  WordnicSqliteTest
//
//  Created by Greg Borenstein on 8/3/14.
//  Copyright (c) 2014 Greg Borenstein. All rights reserved.
//

#import "GABWordnet.h"

@implementation GABWordnet

- (id)init {
    if ((self = [super init])) {
        NSString *sqLiteDb = [[NSBundle mainBundle] pathForResource:@"wordnet30"
                                                             ofType:@"sqlite3"];
        
        if (sqlite3_open([sqLiteDb UTF8String], &_database) != SQLITE_OK) {
            NSLog(@"Failed to open database!");
        } else {
            NSLog(@"Database open.");
        }
    }
    return self;
}

-(NSString*) definitionForWord:(NSString*) word{

    NSString* query = [[NSString alloc] initWithFormat:@"SELECT definition FROM synset where synsetid=(SELECT synsetid FROM sense WHERE wordid=(SELECT wordid FROM word WHERE lemma='%@'));", word];
    
    NSString* result;
    
    sqlite3_stmt *statement;
    if (sqlite3_prepare_v2(_database, [query UTF8String], -1, &statement, nil) == SQLITE_OK) {
        while (sqlite3_step(statement) == SQLITE_ROW) {
            char* defChars = (char *)sqlite3_column_text(statement, 0);
            result = [[NSString alloc] initWithUTF8String:defChars];

        }
        sqlite3_finalize(statement);
    }
    
    
    return result;
    
}

- (void)dealloc {
    sqlite3_close(_database);
}

@end